Rotary hook



C. F. RUBEL July 30, 1940.

ROTARY noon Filed April 21, 1937 (m ulwi 6%? WITNESSES M M W m m M W CPatented July 30, 1940 UNITED STATES PATENT OFFICE ROTARY HOOK porationof Illinois Application April 21, 1937, Serial No. 138,088

10 Claims.

This invention relates to rotary hooks useful by cooperation with theneedles of sewing machines in forming what are commonly known aslockstitch seams.

In the usual types of such hooks, the revolving needle loop-seizing orbook component has an internal circumferential groove of square crosssection which engages, with a snug working fit, an externalcircumferential bearing rib of corresponding cross section on thenon-revolving bohbin case holder. Thus, during the operation or" thesewing machine, excessive heat is generated by friction between theextensive contactingsurfaces of the hook groove and the bobbin caseholder rib, with the result that very rapid wear of the parts takesplace notwithstanding the presence of lubricant, which, of necessity,must be sparingly used to avoid staining or soiling of the thread or ofthe material being sewed.

The purpose of my invention is to overcome the above drawbacks, that isto say, it has for its aim to reduce friction between the relativelyrotating parts of the hook to a minimum with a view toward makingpossible the operation of lockstitch sewing machines at much higherspeeds than attainable heretofore and in turn securing a correspondinglyincreased output from them. These advantages I realize in practice, ashereinafter more fully disclosed, by forming the rib on the bobbin caseholder considerably narrower than ordinarily so that it clears the sidesof the groove in the rotating hook component and by providing the bodyof said rotating component at circumferential intervals with recessesfor confining bearing balls which engage a conformative peripheralraceway in the ribof said bobbin case holder, and, as a consequence,constitute an annular series of spaced contact points to maintain therib centralized in the groove.

In the drawing,

Fig. I is an axial sectional view of a rotary hook convenientlyembodying the present improvements.

Fig. II shows the rotating component of the hook in front elevation withthe stationary component or bobbin case holder and the bobbin caseremoved, and with a .portion broken away to expose one of the bearingballs.

Fig. III is an elevation of the rotating hook component viewed from theleft of Fig. II.

In Figs. I-III of these illustrations the rotating component of myimproved rotary hook is comprehensively designated by the numeral 1; thesame being shown as having a frontally-open hollow annular body 2 whichprpvides a needle 5 loop seizing beak 3 and a 'rearwardly projectingaxial boss or hub l for connection to a drive shaft 5 by means of aplurality of set screws whereof one is indicated at (i. Disposed withinthe hollow of the rotating component! is a non-rotating I0,

cylindric bobbin case holder 1 having an external circumferential rib- 8which extends into an internal circumferential groove 9 in the body 2 ofthe rotating component.

In accordance with my invention, the rib 8 is 13 made considerablynarrower than the groove 9 so that it clears the opposite side walls ofsaid groove as shown in Fig. I. Between the rotating and non-rotatingcomponents I and l of the rotary hook, I interpose a series ofcircumferen- 2 tially-spaced bearing balls it] which are confined incylindric radial cavities H in the body 2 of said rotating component andwhich project somewhat beyond the mouths of the cavities into engagementwith a transversely concaved conformative peripheral raceway E2 in therib 8 of said stationary component. As a consequence of thisinterengagement between the balls It and the raceway E2, the rib 8 ofthe bob-bin case hold-er l is positively maintained centralized in thegroove 9 of the rotating hook component i free of contact with the sidewalls of said groove. The ball cavities l I, it will be observed fromFigs. I and II, are formed jointly by radial openings in the body 2 ofthe rotating hook component I and by segmental backing plates l3 and Mwhich are respectively secured by screws I5 and It to the periphery ofsaid body and which serve as the backing for the balls Hi. In order toprovide for retainment of the balls it by the rotating component I ofthe hook, the edges of the mouths of the cavities H are extendedinwardly somewhat as shown at IT in Figs. I and II. The segmental plate13, may, as illustrated, have the form of a gib with an inwardlyextending flange I8 adapted to underreach a corresponding segmentalextent of the frontal edge of the body 2 of the rotating component I andto form a portion of one side wall of the groove 9, and with an endportion l9 suitably shaped to serve as the loop-shedding tail of therotary hook. The plate M, on the other hand, may provide theloop-deflecting edge at (Fig. III) of the rotary hook, and inconjunction with the beak 3 forms the usual thread-receiving notch orthroat 2| of the hook.

Except for having a ball raceway 12 at the periphery of its rib 8, thebobbin case holder is of customary construction in that it has asegmental frontal flange 23 with a recess 24 for engagement by the usualdetaining or holding finger (not shown) of the sewing machine, and atransverse web or spoke 25 across the back thereof which supports anaxial bobbin case mounting stud 26.

The bobbin case indicated at 21 in Fig. I is likewise of standard formand construction for fitment into the hollow of the bobbin case holder 1with its inwardly-extending axial sleeve projection 28 engaging over thestud 26 of said holder and in turn serving as a support for a freelyrotatable thread spool or bobbin 29.

Due to the interposition of bearing balls which serve as spaced contactpoints between the relatively rotating elements of the rotary hook inthe manner herein set forth, it is evident that I have reduced frictionto a very minimum. My improved rotary hook can thus be operated at muchhigher speeds than hooks of ordinary construction without danger ofoverheating or attendant excessive wear of the parts, thereby not orilymaking possible increased production by the sewing machine in which thehook is used, but doing away with the necessity for the frequentreplacement of Worn parts as heretofore. When required, the bobbin caseholder I can be withdrawn from the body of the rotating hook component 1upon removal of the gib I3 and the three balls associated with thelatter.

While for the purpose of exemplification herein I have shown six bearingballs, this number is to be regarded as arbitrary since, within thescope of the appended claims, it may be increased or decreased as founddesirable or convenient in practice.

Having thus described my invention I claim:

1. A rotary hook for sewing machines comprising a pair of relativelyrotating components one within the other; and a series of bearing ballsconfined in one of said components and projecting into a conformativecircumferential raceway in the other component.

2. A rotary hook for sewing machines comprising a rotatable loop seizingcomponent having a hollow annular body portion with an internalcircumferential groove; a non-rotating bobbin case holder with anarrower external circumferential rib extending into the groove of thehook member and having a ball raceway at its periphery; and bearingballs confined within circumferentially spaced recesses in the annularbody of the rotatable component and engaging the peripheral raceway ofthe rib on the bobbin case holder to keep said rib centralized in saidgroove.

3. A rotary hook for sewing machines comprising a rotatable loop seizingcomponent having a hollow annular body portion with an internalcircumferential groove; 2. non-rotating bobbin case holder axiallywithin the body of the rotating component having an external circunliferential rib which extends into the groove of said rotatablecomponent; and bearing balls within circumferentially spaced radialcavities in the annular body of the rotating component, the edges of themouths of said cavities extending inward slightly to retain the bearingballs with portions of the latter projecting and engaging the peripheryof the circumferential rib of the bobbin case holder.

4. A rotary hook for sewing machines comprising a rotatable loop seizingcomponent having a hollow annular body portion with an internalcircumferential groove; a non-rotating bobbin case holder axially withinthe body of the rotatable component having an external circumferentialrib extending into the groove of said rotatable component; bearing ballsretained within circumferentially-spaced radial openings in the annularbody portion of the rotatable component .and engaging the periphery ofthe circumferential rib on the bobbin case holder; and segmental platemembers on the body of the rotatable component closing the outer ends ofthe ball openings and forming a backing for said balls.

5. In a sewing machine, a rotary hook; a bobbin case with its holderheld from free rotation within the hook, said holder having acircumferential groove externally thereof; and bearing balls confinedfor rotation with the hook and engaging the external groove of thebobbin case holder.

6. A rotary hook for sewing machines comprising a pair of relativelyrotating components, one within the other; and a circumferential seriesof universally rotatable balls confined by one of the components, saidballs providing changing bearing points for the other component; andmeans cooperating with the balls for restricting axial play between thetwo components.

7. A rotary hook for sewing machines comprising a pair of relativelyrotating components, one within the other; and universally rotatableballs confined at circumferential intervals by one of said components,said balls providing changing bearing points for the other components;and means cooperating with the balls for restricting axial play betweenthe two components.

8. A rotary hook for sewing machines comprising a rotating loop seizingcomponent 'with a hollow annular body portion; a non-rotating hollowbobbin case holder axially within the body of said rotatable component;a circumferential series of universally rotatable balls confined by therotating component, said balls providing changing bearing points for thebobbin case holder; and means cooperating with the balls for restrictingaxial play between said component and said bobbin case holder.

9. A rotary hook for sewing machines comprising a rotating loop seizingcomponent having a hollow annular body portion with an internalcircumferential groove; a non-rotating bobbin case holder with anexternal rib extending into the groove of the rotatable component withprovision of clearance at opposite sides thereof; bearing balls confinedwithin circumferentially spaced recesses in the body of the rotatablecomponent, said balls providing changing bearing points for theperiphery of the rib on the bobbin case holder; and means cooperatingwith the balls for restricting axial play of said holder.

10. A rotary hook for sewing machines comprising a pair of relativelyrotating components one within the other; a series of ballscircumferentially interposed between the two components; means formaintaining the balls in uniformly spaced relation; and meanscooperating with the balls to restrict axial play between saidcomponents.

CHARLES F. RUBEL.

